The present invention relates to a valve-position output apparatus for outputting positions of a valve.
With reference to FIG. 8, a conventional valve-position output apparatus will be described. FIG. 8 is a schematic explanatory view of the conventional valve-position output apparatus, wherein FIG. 8(a) shows the state when a valve (not shown) is located at a fully closed valve-position and FIG. 8(b) shows the state when the valve is located at a fully opened valve-position. A pair of first and second arms 02, 03 are attached to a valve shaft 01 of the valve. The valve shaft 01 and the arms 02, 03 are arranged to rotate together in sync with open and close operations of the valve. At the fully closed valve-position shown in FIG. 8(a), the first arm 02 rotates a lever 07 of a limit switch unit 06 counterclockwise to turn on a first limit switch (not shown). On the other hand, at the fully opened valve-position shown in FIG. 8(b), the second arm 03 rotates the lever 07 of the limit switch unit 06 clockwise to turn on a second limit switch (not shown). As described above, the limit switch unit 06 includes the pair of opened valve-position and closed valve-position limit switches. Thus, it is necessary to provide three or four wirings for externally outputting signals from the limit switches.
In the case that a valve-position output apparatus is constructed in such a mechanical structure, it is difficult to sufficiently process data of the valve positions and in particular, to adequately conduct an initial setting in order to accurately detect the valve positions. Further, during open and close operations of the valve, the conflict between the arms 02, 03 and the lever 07 causes an undesirable noise and the wear of the arms 02, 03 and the lever 07. Furthermore, when the valve is moved between the fully opened valve-position and the fully closed valve-position which is spaced apart from the fully opened valve-position at an angle of about 90-degree, the conventional valve-position output apparatus may detect the fully opened and closed valve-positions, but may not detect any valve positions in a transition angle or intermediate angle where the valve is being moved between the fully opened and closed valve-positions.
In order to solve the aforementioned problems, it is an object of the present invention to provide a valve-position output apparatus capable of adequately detecting valve positions on an optical basis.
According to a first aspect of the present invention, there is provided a valve-position output apparatus comprising an interlocking member arranged to move in sync with the open and close operations of a valve, a position detecting aperture formed in the interlocking member, an optical encoder having a light-emitting section and a light-receiving section which are arranged opposed to each other with interposing the interlocking member therebetween, digital valve-position signal generating means for generating a digital valve-position signal on the basis of a signal from the optical encoder, and abnormality determining means for determining an abnormality to generate an alarm signal, by judging whether the valve is located in a transition angle defined between a fully opened valve-position and fully closed valve-position on the basis of the digital valve-position signal from the digital valve-position signal generating means and whether the time period in the transition angle exceeds a predetermined time. The abnormality determining means determines the abnormality when the valve is located in the transition angle for a period of time which exceeds the predetermined time.
In the first aspect of the present invention, the optical encoder is applied to the valve-position output apparatus. This provides reduced mechanical wear of parts and enhanced durability of the valve-position output apparatus. Further, noise arising from operations may be reduced and thereby undesirable noise of the valve-position output apparatus may be sufficiently reduced. Furthermore, contact points or the like may be reduced and thereby undesirable spark or the like may be prevented as least as possible. In addition, any valve positions including those in the transition angle defined between the fully opened and fully closed valve-positions may be readily detected. Since the encoder applied to the present invention is not a magnetic encoder, the valve-position output apparatus of the present invention may not be adversely affected by an external magnetic field and may not go against the external magnetic field.
The valve-position output apparatus of the first aspect of the present invention is also provided with the abnormality determining means. Thus, when the valve is stopped at the valve position in the transition angle, the alarm signal may be output.
According to a second aspect of the present invention, there is provided a valve-position output apparatus comprising an interlocking member adapted to move in sync with open and close operations of a valve, a position detecting aperture formed in the interlocking member, an optical encoder having a light-emitting section and a light-receiving section which are arranged opposed to each other with interposing the interlocking member therebetween, digital valve-position signal generating means for generating a digital valve-position signal on the basis of a signal of the optical encoder, and D/A converting means for converting the digital valve-position signal from the digital valve-position signal generating means into an analog signal. The D/A converting means is arranged to add a certain value to the digital valve-position signal so as not to make the analog signal have a zero value at a fully opened valve-position and fully closed valve-position.
In the second aspect of the present invention, the valve-position output apparatus is provided with the optical encoder. Thus, the effects yielded by the optical encoder are provided as with the valve-position output apparatus of the first aspect of the present invention. In addition, the valve-position output apparatus of the second aspect of the present invention includes the D/A converting means. This allows analog signals to be output despite of applying the optical encoder. Further, since the D/A converting means is arranged to add a certain value to the digital valve-position signal, the output analog signal does not become zero at the fully opened valve-position and fully closed valve-position in a normal state. Thus, when the output analog signal becomes zero, it may be judged as an abnormal state.
According to a third aspect of the present invention, there is provided a valve-position output apparatus comprising an interlocking member arranged to move in sync with open and close operations of a valve, a position detecting aperture formed in the interlocking member, an optical encoder having a light-emitting section and a light-receiving section which are arranged opposed to each other with interposing the interlocking member therebetween, digital valve-position signal generating means for generating a digital valve-position signal on the basis of a signal of the optical encoder, D/A converting means for converting the digital valve-position signal from the digital valve-position signal generating means into an analog signal, and ON-OFF signal generating means for generating ON and OFF signals. The ON-OFF signal generating means generates the ON signal at one of a fully opened valve-position and a fully closed valve-position and generates the OFF signal at the other of the fully opened valve-position and the fully closed valve-position.
In the third aspect of the present invention, the valve-position output apparatus is provided with the optical encoder. Thus, the effects yielded by the optical encoder are provided as with the valve-position output apparatus of the first aspect of the present invention. In addition, the valve-position output apparatus of the third aspect of the present invention includes the D/A converting means and the ON-OFF signal generating means. Thus, this valve-position output apparatus may output the digital valve-position signal, the analog signal and ON-OFF signal, and thereby may cope with various output forms by itself.
According to a fourth aspect of the present invention, there is provided a valve-position output apparatus for a valve arranged to stop at a fully opened valve-position and a fully closed valve-position which is spaced apart from the fully opened valve-position at an angle of about 90 degrees, and to move without any stop motion in a transition angle defined between the fully opened valve-position and the fully closed valve-position. This valve-position output apparatus comprises an interlocking member arranged to move in sync with open and close operations of the valve, a position detecting aperture formed in the interlocking member, an optical encoder having a light-emitting section and a light-receiving section which are arranged opposed to each other with interposing the interlocking member therebetween, digital valve-position signal generating means for generating a digital valve-position signal on the basis of a signal of the optical encoder, and ON-OFF signal generating means for generating ON and OFF signals. The ON-OFF signal generating means generates the ON signal at one of the fully opened valve-position and the fully closed valve-position and generates the OFF signal at the other of the fully opened valve-position and the fully closed valve-position. The valve-position output apparatus further comprises abnormality determining means for determining an abnormality to generate an alarm signal, by judging whether the valve is located in the transition angle defined between the fully opened valve-position and the fully closed valve-position on the basis of the digital valve-position signal from the digital valve-position signal generating means and whether the time period in the transition angle exceeds a predetermined time. The abnormality determining means determines the abnormality when the valve is located in the transition angle for a period of time which exceeds the predetermined time.
In the fourth aspect of the present invention, the valve-position output apparatus is provided with the optical encoder. Thus, the effects yielded by the optical encoder are provided as with the valve-position output apparatus of the first aspect of the present invention. In addition, the valve-position output apparatus of the fourth aspect of the present invention includes the ON-OFF signal generating means and the abnormality determining means. In the conventional valve-position output apparatus arranged to output either one of an ON signal and an OFF signal, when the ON signal or the OFF signal is output, the valve is not always located at the fully opened valve-position or fully closed valve-position, and there is the case that the valve is located at the valve position in the transition angle. However, in the valve-position output apparatus of the fourth aspect of the present invention, the alarm signal is output when the valve is located at the valve position in the transition angle for more than the predetermined time. Thus, when the ON signal or the OFF signal is output and the alarm signal is not output, it may be accurately judged that the valve is located at the fully opened valve-position or fully closed valve-position.
Other features and advantages of the present invention will be apparent from the accompanying drawings and from the detailed description.